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ISL6257: Highly Integrated Battery Charger Controller for Li-Ion/Li-Ion Polymer Batteries


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To study the operation and application of ISL6257 battery charger

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ISL6257: Highly Integrated Battery Charger Controller for Li-Ion/Li-Ion Polymer Batteries

  1. 1. ISL6257: Highly Integrated Battery Charger Controller for Li-Ion/Li-Ion Polymer Batteries <ul><li>Source: Intersil Corporation </li></ul>
  2. 2. Introduction <ul><li>Purpose </li></ul><ul><ul><li>To study the operation and application of ISL6257 battery charger </li></ul></ul><ul><li>Outline </li></ul><ul><ul><li>Overview ISL6257 battery charger </li></ul></ul><ul><ul><li>Functional Block Diagram </li></ul></ul><ul><ul><li>Operation of ISL6257 </li></ul></ul><ul><li>Content </li></ul><ul><ul><li>17 pages </li></ul></ul><ul><li>Duration </li></ul><ul><ul><li>10 Minutes </li></ul></ul>
  3. 3. Overview <ul><li>The ISL6257 is a highly integrated battery charger controller for Li-Ion/Li-Ion polymer batteries. </li></ul><ul><li>The ISL6257 is a narrow VDC (voltage direct current) charger controller for Li-Ion/Li-Ion polymer batteries in notebook computers. </li></ul><ul><li>This Device allows the system to operate from the regulated charger instead of the adapter. </li></ul><ul><li>This device is designed to meet the NVDC-I requirements for better efficiency and longer battery life. </li></ul>
  4. 4. Features <ul><li>+/-0.5% charge voltage accuracy (-10 º C to +100 º C) </li></ul><ul><li>+/-3% accurate battery charge current limit </li></ul><ul><li>+/-25% accurate battery trickle charge current limit </li></ul><ul><li>Fixed 300kHz PWM synchronous buck controller with diode emulation at light load </li></ul><ul><li>AC adapter present indicator </li></ul><ul><li>Fast input current limit response </li></ul><ul><li>Support 2-, 3- and 4-cells battery packs </li></ul><ul><li>Control adapter power source select MOSFET </li></ul><ul><li>Thermal shutdown </li></ul><ul><li>Battery discharge MOSFET control </li></ul><ul><li>Support pulse charging </li></ul>
  5. 5. Functional Block Diagram Pinout
  6. 6. PWM Control <ul><li>A fixed frequency PWM voltage mode control architecture is employed to maintain a constant modulator gain of 11 to achieve fast line regulation as the buck input voltage changes. </li></ul>
  7. 7. Setting the Battery Regulation Voltage <ul><li>A high-accuracy trimmed band-gap voltage reference is used to regulate the battery charging voltage. </li></ul><ul><ul><li>Float VADJ to set the battery voltage </li></ul></ul><ul><ul><ul><li>VCSON = 4.2V × number of the cells </li></ul></ul></ul><ul><ul><li>Connect VADJ to VREF to set 4.41V × number of cells </li></ul></ul><ul><ul><li>Connect VADJ to ground to set 3.99V × number of the cells </li></ul></ul><ul><li>Battery charge voltages can also be set by connecting a resistor divider from VREF to ground. </li></ul>V CELL = 0.175 x V VADJ + 3.99V
  8. 8. Setting the Battery Charge & Input Current Limit Setting the Battery Charge Current Limit The CHLIM input sets the maximum charging current. Setting the Input Current Limit The input current regulator limits the input current by reducing the charging current, when the input current exceeds the input current limit set by ACLIM.
  9. 9. AC/DC Adapter Detection AC Adapter Detection AC Adapter voltage is connected through a resistor divider to ACSET pin to detect AC power is available DC Adapter Detection DC Input is connected through a resistor divider to DCSET pin to detect the lower voltage DC power available. ISL6257
  10. 10. Specification LDO Regulator VDD provides a 5.0V supply voltage from the internal LDO regulator from DCIN and can deliver up to 30mA of current. <ul><li>Shutdown </li></ul><ul><li>The ISL6257 features a low-power shutdown mode. Driving EN low shuts down the ISL6257. </li></ul><ul><li>In shutdown, the DC/DC converter is disabled, and VCOMP and ICOMP are pulled to ground. </li></ul>
  11. 11. Snubber Design ISL6257 operates in discontinuous current mode (DCM), when the load current is less than half the P-P current in the inductor, after the low side FET turns-off the phase voltage rings due to high impedance with both FETs off. A snubber circuit (resistor in series with capacitor) from phase node to ground can reduce the rings. PHASE 10V/div INDUCTOR CURRENT 1A/div UGATE 5V/div
  12. 12. Adapter Current Limit Control Loop ISL6257 will reduce the current to battery or output voltage to hold the adapter current at the limit set by ACLIM pin. A filter is added between RS1 and CSIP and CSIN to reduce the switching noise. The filter roll off frequency should be between the cross over frequency and the switching frequency.
  13. 13. Voltage Control Loop
  14. 14. Charge Current Control Loop
  15. 15. External Components Selection Inductor Selection Output Capacitor Selection MOSFET Selection Practical inductor design is based on the inductor ripple current being ±15% to ±20% of the maximum operating DC current at maximum input voltage. Required inductance can be calculated using the below equation. This capacitor is used to absorb the high frequency switching ripple current and supply very high di/dt load transient. It is selected using the equation given. The high-side MOSFET must be able to dissipate the conduction losses plus the switching losses.
  17. 17. Additional Resource <ul><li>For ordering the ISL6257, please click the part list or </li></ul><ul><li>Call our sales hotline </li></ul><ul><li>For additional inquires contact our technical service hotline </li></ul><ul><li>For more product information go to </li></ul><ul><ul><li>,1477,ISL6257,00.html#longdesc </li></ul></ul>Newark Farnell